Gas-fractionating system



Jan. 5, 1960 H. MULDER GAS-FRACTIONATING SYSTEM 5 Sheets-Sheet 1 Filed March 27, 1956 FIG.1

INVENTR HERMAN MULDER AGENT Jan. 5, 1960 H. MULDER GAS-FRACTIONATING SYSTEM 3 Sheets-Sheet 2 Filed March 27, 1956 INVENTOR HERMAN MULDER flfif AGENT Jan. 5, 1960 H. MULDER 2,9l9,556

GAS-FRACTIONATING SYSTEM Filed March 27, 1956 3 Sheets-Sheet 3 FIG.4

INVENTQR HERMAN' 4959555 V AGENT United tates GAS-FRACTIONATING SYSTEM Herman Mulder, Eindhoven, Netherlands, assignor, by

mesne assients, to North American Philips Con:- pany, Inc., NewYork, N.Y., a 'corporation of Delaware Application March 27, 1956, Serial No. ?74,149

y Claims priority, application Netherlands March 30, 1955 .Claims. (Cl. 62-42) This invention relates to gas-fractionating systems comprising a boiler for the fraction of high boiling point and a source of cold by means of which at least part of the fraction of low boilng point is condensed, said condensed liquid being partially supplied to the column from the source of cold through a down-pipe and a following rise pipe in which a vapour bubble pumping fraction is maintained which depends upon the level of the liquid in the boiler, and another part being drawn off from the system.

In gas-fractionating systems it has been proposed to regulate the amount of washing liquid supplied to the column in accordance with the liquid level in the boiler. Upon a rise of said level the amount of washing liquid has to be reduced and in the case of a drop of the level the amount of washing liquid has to be increased. This may be efiected by providing the system with two rise pipes in both of which a vapour bubble pumping action is maintained. Through one rise pipe a part of the fraction of low boiling point is supplied as washing liquid to the column and through the other rise pipe another part is carried ofi from the system, the pumping action depending upon the level of the liquid in the boiler.

It has been found that if the system comprises a down-ppe followed by a rise pipe for the supply of the fraction of low boiling point to the column, in which a vapour bubble pumping action is maintained, a different solution may advantageously be resorted to.

In accordance with the invention the down-pipe comprises means at the height of the normal liquid level, by which the amount of the low-boiling fraction is determined, which is carried off as liquid from the system.

Said means may be as follows. For example, it is possible to mount an electrc resistive wire in the downpipe, the resistance of which varies upon a rise of the liquid level. Said resistance variation may serve in a known manner as a control factor for a cock determining either the quantity of washing liquid supplied to the column or the quantity carried oi from the system.

As an alternative, the down-pipe may comprise a float, the position of which determines the amount of washing liquid supplied to the column through a transmission mechanism.

In a simple embodiment of the invention, said means consist of an outlet port flush with the normal level of the liquid. When this level rises a larger amount of condensed liquid is carried off from the system through said outlet port.

In a further embodiment of the invention, an outlet conduit comprising a liquid lock leads to the outlet port. Said liquid lock permits the amount of condensed liquid to be carried off in accordance with the production of cold by the source of cold, while in the system a subatmospheric pressure can be maintained by means of which the gas-mixture to be separated is drawn in.

A further embodiment of the invention comprises means which, when the level of the liquid rises in the boiler, permits the quantity of thermal energy producing the vapour bubble pumping action to be reduced.

Said means can be realized in various manners. Thus, for example, the thermal energy may be supplied to a rise pipe with the aid of an element of good thermal conductivity, one end of which is secured to the rise pipe and the other end of which is secured to a hotter part of the system.

In this case the boiler comprises an overflow with the aid of which the cold liquid is supplied to the element if the level in the boiler rises, with the result that this element is cooled locally and the vapour-bubble pumping action diminshes.

As an alternative, the boiler may be connected to the column through two pipe connections for the vapour, one of said pipe connectons opening into the boiler at a lower point than does the other and the rise pipe being in heat-exchanging contact with saidppe connection. When the liquid level rises in the boiler said pipe connection is closed so that less thermal energy is supplied to the rise pipe.

In order that the invention may be readily carried into efiect it will now be described in detail, by way of example, with reference to the accompanying drawings, in which Figs. 1 and 2 represent a gas-fractionating system in which condensed liquid is carried ofl:` at the height of the normal liquid level in the down-pipe.

In Fig. 3, a cock is controlled by means of electric resistive wire provided at the height of the level in the down-pipe.

Fig. 4 shows a gas refrigerator.

The system shown in Figures l and 2 comprises a gasfractionating column 1 with a boiler 2, which parts are separated from each other by a partition 3. 'From the wall 3 a pipe 4 extends into the liquid of the boiler 2. The boiler is furthermore connected with the column through two pipe connections 5 and 6 respectively, which are connected together through the conduit 7, and through the conduit 8. The conduit 8 comprises a cock 9 which permits the resistance between the boiler and the column to be regulated. The boiler furthermore comprises a pipe 10 which overtops the liquid inside the boiler and passes through the bottom 11 of the boiler. The pipe 10 is externally fumshed with a number of fins 12. with openings 13 which do not register and the fins are surrounded by a wall 14 so that a heat-exchanger is formed. Said heat-exchanger comprises a supply conduit 15 and an outlet conduit 16 which opens into the column at some distance from its bottom end. At the top of the column is provided a conduit 17 which is connected to a gas refrgerator 19 through a conduit 18. Said gas refrigerator s of the normal type and driven from an electrc motor 20. The conduit 17 is connected with a down part 21 terminating in a receptacle 22 which carries a rise pipe 23 opening into the column at its upper end. Said rise pipe is connected through a heat-transferring strip 24 to the pipe connection 6 which opens into the boiler at a lower point than does the pipe connection 5 and is closed at its lower end but has a number of lateral openngs 25.

In the down pipe 21, the liquid level will be flush with the line 25 under normal Operating conditions. Above the said normal liquid level is provided an outlet port 27 opening into an outlet pipe 28 with a liquid lock 29. Under said outlet pipe a receptacle 30 is placed.

The system operates as follows:

Due to the reproduction of cold by the gas refrigerator l@ and the presence of the liquid lock 29 a sub-atmospheric pressure is produced in the column, with the result that the gas mixture to be separated, for example air, is drawn in through the conduit 15. The air is in heatevaporates in the boiler. is described, for example, in Belgian patent spec. 527,602.

exchanging contact with the fins 12 so that it is cooled and any impurities of the mixture, such as water vapour and carbonic acid, are frozen out. The thermal energy withdrawn from the air is transferred through the conduit 10 to the bottom 11 of the boiler 2 with the result that the high-boiling fraction, that is to say oxygen, A heat exchanger of this type The air thus cooled and purified ows through the conduit 16 to the column in which it is fractionated. The nitrogen flows through conduits 17 and 18 to the gas refrigerator 19 with the aid of which this fraction is condensed. The condensate flows through the conduit 18 into the down-pipe 21 so that a liquid column with a level 26 forms in said pipe under normal operating conditions. The nitrogen is pumped up in the conduit 23 as a result of a vapour bubble pumping action, thereby supplying the nitrogen in the form of washng liquid to the column. The thermal energy required for the vapour bubble pumping action is supplied by the vapour flowing through the pipe connection 6 which is in heat-cxchanging contact with the rise pipe 23 via the strip 24.

The outlet opening 27 is provided at such a height in the down pipe that under normal conditions the desired quantity of liquid nitrogen is carried oti, which liquid is collected in the receptacle 30. Under normal Operating conditions the quantity of washing liquid supplied to the column is such that the quantity of liquid rich in oxygen, which is supplied through the pipe 4 to the boiler, is sutficient to cause the liquid level in the boiler to drop not too far below the conduit 6. If the liquid level is below the conduit 6 oxygen-nitrogen vapour rich in oxygen flows both through the conduit 5 and through the conduit 6. Because of the liquid level in the boiler the conduit 6 becomes gradually closed with the result that the oxygen concentration in the conduit 6 is reduced and the nitrogen concentration is increased, thereby decreasing the amount of thermal energy supplied via the strip 24 to the rise pipe 23 so that the vapour-bubble pumping action likewise decreases and less washing liquid is supplied to the column, hence a lesser amount of liquid rich in oxygen flows into the boiler.

A decrease of the vapour bubble pumping action results, however, in a rise of the liquid level in the down pipe 21 so that more liquid is cam'ed o through the opening 26 and the outlet conduit 27 comprising the liquid lock 28. By controlling the cock 9 in the conduit 8 the pressure of the boiler 2 can be made sufficiently high to blow-off part of the oxygen vapour through the pipe 10 from the system, the vapour assisting in cooling the air flowing to the system. During the time the tube 6 is closed by the liquid, oxygen vapour naturally still flows through the pipe connection 5, which opens at a higher point into the boiler, to the column.

In Fig. 3, parts corresponding to those of Figs. l and 2 are designated by the same reference numerals. The gas-mxture to be fractionated, for example air, is again drawn in through the conduit and cooled by the fins 12, undesired constituents being deposited on said fins. The purified air again flows through the conduit 16 to the column in which it is fractionated. The low-boiling fraction, that is to say nitrogen, flows through conduts 17 and 18 to the gas refrigerator 19 inwhich it is condensed, the condensate being carried off through the conduit 18 and the down pipe 21 to the receptacle 22 carrying the n'se tube 23. In the down pipe 21 the nitrogen is at the height of the line 26 under normal conditions.

In the rise pipe 23 a Vapour-bubble pumping action is maintained. For this purpose provision is made of a strip 24 which is in heat-exchanging contact with one end of an element 31, the other end of which is Secured to a wall 14 so that the upper end of this element has a considerably lower temperature than has its lower end and an amount of thermal energy is supplied through said element to the nitrogen in the rise tube, thus producing a vapour-bubble pumping action. The wall 3 between the column and the boiler has a narrow port 32 through which at least a part of the vapour produced in the boiler is supplied to the column. The port 32 has such a Capacity that the pressure in the boiler exceeds atmospheric pressure so that another part of the vapour can be blown off from the system through the conduit 10. The boiler has an overfiow 33 through which passes he element 31 provided with fins 34 in situ.

At the height of the normal liquid level 26 in the down pipe 21 there is provided a resistive wire 35 which extends partly above and partly below the liquid level. Said resistive wire forms part of a regulating mechanism 36 and 37 controlling a cock 33 in an outlet conduit 39 of the gas refrigerator.

Upon the liquid level rising in the boiler 2 a small amount or" liquid comes in heat-exchanging contact with the fins 34 of the elements 31 through the overfiow 33, so that said element is locally cooled and the flow of thermal energy through said element to the rise pipe 23 is reduced. This results in that the liquid level rises in the down pipe 21 and the amount of washing liquid supplied to the column is reduced. As a result of the rise of the liquid level in the down pipe 21 the resistance of the resistive wire 35 changes. Said resistance variation may bring about in a known manner, through the regulating mechanism 36, 37, adjustment of the cock 38, so that more liquid is carried off via the pipe 39 of the gas refrigerator 19.

The aforesaid embodiments comprise a gas refrigerator in the form of a displacer engine. The term gas refrigerator is here to be understood to mean a socalled refrigerator Operating according to the reversed hot-gas engine principle. Said engines may, as is known, be constructed in various manners, for example as a displacer engine, as a double-acting engine, as an engine whose cylinders subtend an angle, or as an engine, the working chamber of which is combined with that of a hot-gas engine. Engines of these types also can be used in the system in accordance with the invention. It will be appreciated that the invention may alternatively be used if the cold is produced in a different manner but, in general, this will complicate the system with respect to the systems referred to above in which the column is a single column and operates practically at atmospheric pressure.

The height of the liquid level in the down-pipe 21 cannot only be measured with the aid of an electrical resistive wire but also by other means, for example, by means of a float deviee in which the level of the fioat is a measure of the amount of liquid nitrogen carried off from the system. As an alternative, the height of the column may be measured in a different manner, for example with the aid of the pressure prevailing at the bottom of the receptacle 22. Naturally, the device shown in Fig. 3 may be used for controlling the quantity of liquid inside the boiler in combination with the outlet port 27 shown in Fig. 1. Conversely, the device shown in Fig. 1 may be used for the liquid-measuring device represented in Fig. 3.`

Pig. 4 shows a form of gas refrigerator suitable for use in the present system. The engine comprises a cylinder 40 in which a displacer 41 and a piston 42 reciprocate harmonically with a substantially harmonic phase dierence. To this end the displacer .41 is coupled through a driving-rod system 43 to a crank of a crank shaft 44, the pisten 42 being coupled through a drivingred system 45 to cranks of the same crank shaft. The space 46 above the displacer 41 is the so-called expansion chamber which is connected through a freezer 47, a regenerator 48 and a cooler 49 with a compression chamber 50 between the displacer and the piston. The refrigerator is driven from an electric motor 51 and as a result of the reciprocating motion of the displacer and of the freezer. I condenser chamber 52 in which a' gas, for example the the piston a gas, for example hydrog'en or helium, per- .torms a thermo-dynamic cycle in the engine so that cold is 'produced' and another medium can be cooled by means To this end provision is made of a nitrogen from a gas-fractionating column, is condensed.

Similarly to Figures l and 2, said nitrogen is supplied through the conduit`18 to the condenser chamber 52, the condensed liquid Iikewise being carried off through the i conduit 18. i What is clained is:

1. A gas-fractionating system for separating a gaseous mixture comprising a column having a hoiler, partition 'means separating said column from said boiler, said boiler having said high boiling fraction, means for producng and supplying a source of cold, means conducting at least a part of the low boiling fraction to said source of cold to be condensed, a downwardly directed pipe for at least partially supplying said condensed liquid to said column, an upwardly directed pipe adjacent to said downwardly directed pipe, a substantially horizontal receptacle for the `condensed liquid connecting said upwardly and downwardly directed pipes, both of said pipes being external of said column, means providing a vapor bubble pumping action in said upwardly directed pipe dependent upon the liquid level in said boiler, and

means 'for discharging part of the low boiling fraction from the system including and dependent upon a device for 'determining the quantity of said discharged part which in turn is dependent upon the liquid level in said downwardly directed pipe.

2. A gas fractionating system for separating a gaseous mixture as claimed in claim 1 further comprising means for reducing the amount of thei-mal energy which produces the vapor bubble pumping action upon an increase in the liquid level in the boiler.

3. A gas fractonating system for separating a gaseous mixture comprising a column having a boiler, partition means separating said column from said boiler, said boiler having a boiling fraction, means for producing and supplying a source of cold, means conducting at least a part of the low boiling fraction to said source of cold to be condensed, a downwardly directed pipe for at least partially supplying said condensed liquid to i i said column, an upwardly directed pipe adjacent to said regulating means controlling the amount of liquid discharge from said cold source operatively connected to said resistance wre whereby said liquid level in said downwardly directed pipe causes changes in the resistance in said resistance wire to thereby control the operation of said regulating means.

. 4. A gas fractoning system for separating a gaseous mixture comprising a column having a boiler, partition means separating said column for said boiler, said boiler having a high boiling fraction, means for producng and supplying a source of cold, means conducting at least a part of the low boiling fraction to said source of cold to be condensed, a downwardly directed pipe for at least partially supplying said condensed liquid to said column, an outlet part in said downwardly directed pipe at the height of the normal liquid level therein, an upwardly directed pipe adjacent to said downwardly directed pipe, a substantially horizontal receptacle for the condensed liquid connecting said upwardly and downwardly directed pipes, both of said pipes being external of said column, means providing a vapor bubble pumping action in said upwardly directed pipe dependent upon the liquid level in said boiler, and means for discharging part of the low boiling fraction from the system including and dependent upon a device for determining the quantity of said discharged part which in turn is dependent upon the liquid level in said downwardly directed pipe.

5. A gas fractonating system for separating a gaseous mixture comprising a column having a boiler, partition means separating said column from said boiler, said boiler having a high boiling fraction, means for producing and supplying a source of cold, means conducting at least a part of the low boiling fraction to said source of cold to be condensed, a downwardly directed pipe for at least partially supplying said condensed liquid to said column, an upwardly directed pipe adjacent to said downwardly directed pipe, a substantially horizontal receptacle for the condensed liquid connecting said upwardly and downwardly directed pipes, both of said pipes being external of said column, means providing a vapor bubble pumping action in said upwardly directed pipe dependent upon the liquid level in said boiler, means for discharging part of the low boiling fraction from the system including and dependent upon a device for determining the quantity of said discharged part which in turn is dependent upon the liquid level in said downwardly directed pipe, an outlet part in said downwardly directed pipe at the height of the normal liquid layer therein, and an outlet conduit connected to said outlet part and having a liquid lock therein.

References Cited in the file of this patent UNITED STATES PATENTS 2,127,0 04 Nelson Aug. 16, 1938 2,236,966 Balthis Apr. 1, 1941 2,541,409 Cornelius Feb. 13, 1951 2,619,814 Kniel Dec. 2, 1952 2,650,482 Lobo Sept. 1, 1953 2,762,208 Dennis Sept. 11, 1956 2,764,536 Hutchns Sept. 25, 1956 2,799,141 Jonkers July 16, 1957 

